Photographic film comprises a light sensitive coating on a polymeric support. Since about 1930 one support material has been cellulose triacetate (sometimes referred to as cellulose acetate). During the manufacture of cellulose acetate-based photographic film, a certain amount of waste is generated, either during the casting of the support and application of gelatin subbing and backside layers, or during application of the sensitizing layers. In addition, once the film has been used it is possible to recover the support material for reuse of the polymer by separating the light sensitive coating from the polymer support and then treating the support. Given the cost of virgin cellulose acetate, it is economically beneficial to recycle any cellulose acetate support that fails to meet specifications for one reason or another. Numerous ways have been devised for recovery of cellulose acetate supports.
Research Disclosure Item 12629, published October 1974, Research Disclosure Item 19634, published August 1980, U.S. Pat. Nos. 1,844,711, 3,956,088 and 5,500,328 describe some techniques for treating film supports to recover cellulose acetate.
The recycling or recovery operation involves the chemical stripping and removal of all layers from the cellulose acetate-base to make it fit for reuse. Support that has been so treated is called recycled acetate support.
Cellulosic film support used for consumer films can build up static charge when transported through coating machines during manufacture or through cameras during use. This static charge can discharge and fog the light sensitive emulsion layers, hence, the need for static protection. Since photographic films are used under a variety of humidity conditions, it would be advantageous to use a humidity independent antistatic agent to maximize static protection. If some antistatic agents are not protected from photographic processing solutions, however, they can lose their conductivity and the film is prone to pick up dust which leads to white spots on prints. A protected antistatic agent, in turn, would maintain its conductivity after processing and reduce or eliminate white spots on prints.
Another problem associated with processing of photographic films is that of scum formation. Sources of the scum include residual processing solution or salt deposits from hard water. A backing layer that minimizes the formation of scum and reduces the need to clean the negatives before printing is highly desirable.
The incorporation of a lubricant in a backing layer improves the transport of the support or film through production equipment and cameras and is highly desirable.
Thus, there exists a need for a backing system for photographic elements which provides all of the above-mentioned features. The present invention describes a two or three layer backing for a photographic element which includes a cellulose acetate support, an antistatic layer which is process survivable, a barrier layer comprising a water-insoluble polymer and preferably an overcoat lubricant layer. The backing system of the present invention provides antistatic protection for cellulose acetate films and is removable thereby allowing recycling of the cellulose acetate support.